A spoiler is a lift dumping device typically provided on the upper aerodynamic surface of an aircraft wing between the main fixed wing and a trailing edge flap. The flap is typically moveable between a retracted position and one or more extended positions for increasing the maximum lift coefficient of the wing. The flap deployment typically comprises a downward deflection, which may be effected by a downward rotary movement and/or a movement in the aft/downward direction with respect to the fixed wing.
A conventional spoiler typically moves between a retracted (0 degree) cruise position and an upwardly extended (positive rotation angle) lift dump position. A so-called “droop spoiler” can also be moved to a downwardly extended (negative rotation angle) drooped position when the flap is partially or fully deployed, so as to manage a gap between the spoiler and the flap. Managing this gap can significantly improve the aerodynamic performance of the wing in a high lift configuration.
Legacy aircraft with a drooping spoiler configuration may have a mechanical linkage between the spoiler and flap, such that the drooping motion of the spoiler and flap are synchronised. This mechanical linkage adds unnecessary weight. Fly-by-wire control systems on modern aircraft allow for independent actuation of the spoiler and flap actuators with control rules to link the flap and spoiler movement.
Under normal operation, the control systems effectively manage the flap and spoiler motion. However, in the event of failure of the spoiler actuator, or its control system, the spoiler could remain in its drooped position whilst the flap is being retracted. Since the drooped spoiler partially occupies the position vacated by the deployed flap there exists the possibility that an attempt to fully retract the flap following this spoiler actuator/control failure may cause a clash between the leading edge of the retracting flap and the trailing edge of the drooped spoiler, which is highly undesirable.
EP1843943 proposes a solution in which the spoiler and flap movement is configured such that the retracting flap will contact the underside of the drooped spoiler following a spoiler control failure, and by direct mechanical contact the retracting flap will move the spoiler from its drooped position to its cruise (0 degree) position accompanied by back-driving the spoiler actuator.
Whilst the solution presented in EP1843943 may be adequate under some circumstances it does not allow for a flap and spoiler configuration in which the retracting flap could contact the spoiler trailing edge “end-on”, which could cause a jam between the flap and spoiler, thus preventing the flap retraction, and possible damage to the spoiler and/or flap.